I`m currently working on Minecrafts noteblock sounds, replacing them with different instruments and so on. This works quite well and sounds good so far.
My only problem is Minecrafts behavior with tuning: since it just changes the pitch of each sample the instruments immediately sound pretty ridiculous. Does somebody know if there is a way to "tell" Minecraft to use a different sample-version for every pitch? Its probably rather hidden within the code itself and not so easily changeable with a simple resource pack, right?
However, I don`t fully get your suggestion. A custom sounds.json file lets me add or change the played soundfiles for the noteblocks, but I don`t see (yet) a way to call tuning related audio files from there and stop the pitching. But maybe I`m just overlooking something, I`m really not an expert in this